Melanie L Yarbrough1, Kelleigh E Briden2, John V Mitsios1, Annette L Weindel3, Cindy M Terrill2, David A Hunstad4, Dennis J Dietzen5. 1. Departments of Pathology and Immunology, School of Medicine, Washington University, St. Louis, Missouri, USA. 2. Departments of Pediatrics, School of Medicine, Washington University, St. Louis, Missouri, USA. 3. St. Louis Children's Hospital, St. Louis, Missouri, USA. 4. Departments of Pediatrics, School of Medicine, Washington University, St. Louis, Missouri, USA; Departments of Molecular Microbiology, School of Medicine, Washington University, St. Louis, Missouri, USA. 5. Departments of Pathology and Immunology, School of Medicine, Washington University, St. Louis, Missouri, USA; Departments of Pediatrics, School of Medicine, Washington University, St. Louis, Missouri, USA. Electronic address: dietzen_d@wustl.edu.
Abstract
BACKGROUND: Indoleamine-2,3-dioxygenase (IDO) catalyzes the first step of tryptophan (Trp) catabolism, yielding kynurenine (Kyn) metabolites. The kynurenine-to-tryptophan (K/T) ratio is used as a surrogate for biological IDO enzyme activity. IDO expression is increased during Escherichia coli urinary tract infection (UTI). Thus, our objective was to develop a method for measurement of Kyn/Trp ratio in human blood and urine and evaluate its use as a biomarker of UTI. METHODS: A mass spectrometric method was developed to measure Trp and Kyn in serum and urine specimens. The method was applied to clinical urine specimens from symptomatic pediatric patients with laboratory-confirmed UTI or other acute conditions and from healthy controls. RESULTS: The liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was linear to 500 μmol/L for both Trp and Kyn. Imprecision ranged from 5 to 15% for Trp and 6-20% for Kyn. Analytical recoveries of Trp and Kyn ranged from 96 to 119% in serum and 90-97% in urine. No correlation was found between the K/T ratio and circulating IDO mass (r = 0.110) in serum. Urinary Kyn and Trp in the pediatric test cohort demonstrated elevations in the K/T ratio in symptomatic patients with UTI (median 13.08) and without UTI (median 14.38) compared to healthy controls (median 4.93; p < 0.001 for both comparisons). No significant difference in K/T ratio was noted between symptomatic patients with and without UTI (p = 0.84). CONCLUSIONS: Measurement of Trp and Kyn by LC-MS/MS is accurate and precise in serum and urine specimens. While urinary K/T ratio is not a specific biomarker for UTI, it may represent a general indicator of a systemic inflammatory process.
BACKGROUND:Indoleamine-2,3-dioxygenase (IDO) catalyzes the first step of tryptophan (Trp) catabolism, yielding kynurenine (Kyn) metabolites. The kynurenine-to-tryptophan (K/T) ratio is used as a surrogate for biological IDO enzyme activity. IDO expression is increased during Escherichia coli urinary tract infection (UTI). Thus, our objective was to develop a method for measurement of Kyn/Trp ratio in human blood and urine and evaluate its use as a biomarker of UTI. METHODS: A mass spectrometric method was developed to measure Trp and Kyn in serum and urine specimens. The method was applied to clinical urine specimens from symptomatic pediatric patients with laboratory-confirmed UTI or other acute conditions and from healthy controls. RESULTS: The liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was linear to 500 μmol/L for both Trp and Kyn. Imprecision ranged from 5 to 15% for Trp and 6-20% for Kyn. Analytical recoveries of Trp and Kyn ranged from 96 to 119% in serum and 90-97% in urine. No correlation was found between the K/T ratio and circulating IDO mass (r = 0.110) in serum. Urinary Kyn and Trp in the pediatric test cohort demonstrated elevations in the K/T ratio in symptomatic patients with UTI (median 13.08) and without UTI (median 14.38) compared to healthy controls (median 4.93; p < 0.001 for both comparisons). No significant difference in K/T ratio was noted between symptomatic patients with and without UTI (p = 0.84). CONCLUSIONS: Measurement of Trp and Kyn by LC-MS/MS is accurate and precise in serum and urine specimens. While urinary K/T ratio is not a specific biomarker for UTI, it may represent a general indicator of a systemic inflammatory process.
Authors: Vikas R Dharnidharka; Eihab Al Khasawneh; Sushil Gupta; Jonathan J Shuster; Douglas W Theriaque; Amir H Shahlaee; Timothy J Garrett Journal: Transplantation Date: 2013-09 Impact factor: 4.939
Authors: Timothy J Straub; Wen-Chi Chou; Abigail L Manson; Henry L Schreiber; Bruce J Walker; Christopher A Desjardins; Sinéad B Chapman; Kerrie L Kaspar; Orsalem J Kahsai; Elizabeth Traylor; Karen W Dodson; Meredith A J Hullar; Scott J Hultgren; Christina Khoo; Ashlee M Earl Journal: BMC Microbiol Date: 2021-02-18 Impact factor: 3.605